[GRASS-user] v.extract -d vs. v.dissolve

[Nikos Alexandris]

On Sun, 2008-11-09 at 15:34 -0800, Hamish wrote:
> Nikos Alexandris
> > What could be the reason for v.dissolve failing to dissolve when
> > v.extract -d works just fine with the exact same vector maps? Bug?
> 
> is there a table attached?
> 
> 
> without specific details of command, map, and result it is rather hard to
> guess.....
> 
> 
> Hamish

Hamish,
apologies!

Here you go (working with grass-6.4.svn):

#info of vector map
v.info fgaps_shadows_singleid_patched_nik -c

Displaying column types/names for database connection of layer 1:
INTEGER|cat
INTEGER|value
CHARACTER|label
## column "value" contains just 1's, 2's, 3's, 4's and 5's

# dissolving
v.dissolve fgaps_shadows_singleid_patched_nik
out=fgaps_shadows_singleid_patched_nik_dissolved_test column=value

 100%
Building topology for vector map
<fgaps_shadows_singleid_patched_nik_dissolved_test_14997>...
54377 primitives registered            
629349 vertices registered
Building areas:  100%
38049 areas built      
24046 isles built
Attaching islands:  100%
Attaching centroids:  100%
Topology was built
Number of nodes     :   40374
Number of primitives:   54377
Number of points    :   0
Number of lines     :   0
Number of boundaries:   47093
Number of centroids :   7284
Number of areas     :   38049
Number of isles     :   24046
Number of areas without centroid :   30765
7284 features reclassed
Building topology for vector map
<fgaps_shadows_singleid_patched_nik_dissolved_test>...
54377 primitives registered            
629349 vertices registered
Building areas:  100%
38049 areas built      
24046 isles built
Attaching islands:  100%
Attaching centroids:  100%
Topology was built
Number of nodes     :   40374
Number of primitives:   54377
Number of points    :   0
Number of lines     :   0
Number of boundaries:   47093
Number of centroids :   7284
Number of areas     :   38049
Number of isles     :   24046
Number of areas without centroid :   30765
Removing duplicate centroids...
Building topology for vector map
<fgaps_shadows_singleid_patched_nik_dissolved_test>...
54377 primitives registered            
629349 vertices registered
Building areas:  100%
38049 areas built      
24046 isles built
Attaching islands:  100%
Attaching centroids:  100%
Topology was built
Number of nodes     :   40374
Number of primitives:   54377
Number of points    :   0
Number of lines     :   0
Number of boundaries:   47093
Number of centroids :   7284
Number of areas     :   38049
Number of isles     :   24046
Number of areas without centroid :   30765

# add table to database
v.db.addtable fgaps_shadows_singleid_patched_nik_dissolved_test

Using vector map name as table name:
fgaps_shadows_singleid_patched_nik_dissolved_test
Creating new DB connection based on default mapset settings...
Creating table with columns (cat integer)
The table <fgaps_shadows_singleid_patched_nik_dissolved_test> is now
part
of vector map <fgaps_shadows_singleid_patched_nik_dissolved_test> and
may
be deleted or overwritten by GRASS modules
Select privileges were granted on the table
Updating database...
 100%
5 categories read from map
4 categories read from map don't exist in selection from table
4 records updated/inserted
Current attribute table links:
Vector map <fgaps_shadows_singleid_patched_nik_dissolved_test at nik> is
connected by:
layer <1> table <fgaps_shadows_singleid_patched_nik_dissolved_test> in
database </home/nik/grassdb/rlp_fgaps/gk2_option6/sqlite.db> through
driver <sqlite> with key <cat>
## only 4 records updated!? ##

# checking columns
v.info fgaps_shadows_singleid_patched_nik_dissolved_test -c

Displaying column types/names for database connection of layer 1:
INTEGER|cat
## why is the rest lost?

# using v.extract ## but this is probably not what I want. I need to
"dissolve" based on "value" column!
v.extract -d fgaps_shadows_singleid_patched_nik
out=fgaps_shadows_singleid_patched_nik_dissolved_test2

Building topology for vector map
<fgaps_shadows_singleid_patched_nik_dissolved_test2>...
54377 primitives registered            
629349 vertices registered
Building areas:  100%
38049 areas built      
24046 isles built
Attaching islands:  100%
Attaching centroids:  100%
Topology was built
Number of nodes     :   40374
Number of primitives:   54377
Number of points    :   0
Number of lines     :   0
Number of boundaries:   47093
Number of centroids :   7284
Number of areas     :   38049
Number of isles     :   24046
Number of areas without centroid :   30765
v.extract complete.
Removing duplicate centroids...
Building topology for vector map
<fgaps_shadows_singleid_patched_nik_dissolved_test2>...
54377 primitives registered            
629349 vertices registered
Building areas:  100%
38049 areas built      
24046 isles built
Attaching islands:  100%
Attaching centroids:  100%
Topology was built
Number of nodes     :   40374
Number of primitives:   54377
Number of points    :   0
Number of lines     :   0
Number of boundaries:   47093
Number of centroids :   7284
Number of areas     :   38049
Number of isles     :   24046
Number of areas without centroid :   30765

# checking columns
v.info fgaps_shadows_singleid_patched_nik_dissolved_test2 -c

Displaying column types/names for database connection of layer 1:
INTEGER|cat
INTEGER|value
CHARACTER|label